This dissertation focused on the development of sustainable Pd-based catalysts for the removal of waterborne contaminants (i.e., nitrite and nitrate). It explored different catalyst supports, including electrospun polyacrylonitrile (PAN) nanofibers (NFs), electrospun carbon nanofibers (CNFs), and graphitic carbon nitride (g-C3N4), which were underexplored for environmental engineering applications. Catalytic kinetics, selectivity (ammonia vs. nitrogen), and longevity for contaminant reduction were evaluated. Extensive instrumental analyses (e.g., scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS)) were also conducted to identify key catalyst properties that determine catalytic performance. These Pd-based catalysts are effective, robust, and sustainable, and therefore they hold promise for water decontamination. The following topics were included in this dissertation: (1) Electrospun PAN Nanofiber Supported Pd Catalyst Composites for Water Decontamination; (2) Enhancement of Nitrite Reduction Kinetics on Electrospun Pd-Carbon Nanomaterial Catalysts for Water Purification; (3) g-C3N4 Supported Ultrafine Pd and Pd-Cu Catalysts: Enhanced Reactivity, Selectivity, and Longevity for Nitrite and Nitrate Hydrogenation.